With the remarkable progress in the technique of the electronic industry, there is an increasing need for higher density and higher performance of a printed circuit board, and a demand for such printed circuit board is also increasing. In particular, in a motherboard for latest digital equipment, such as mobile phones, notebook computers or digital cameras, there is an increasing need for higher density and miniaturization as the motherboard is reduced in size and thickness. On the other hand, there is also an increasing need for higher connection reliability than before.
Among currently employed packaging techniques, a semi-additive method and a full additive method are most extensively used.
In the semi-additive method, a board is first coated with a catalyst. An electroless plating film then is formed as an underlying layer for current conduction for electrolytic plating. Using a plating resist exposing portions which later form a pattern for interconnections as a mask, an electrolytic plating film, which later becomes a pattern for interconnections, is formed by electroplating for circuit pattern forming.
In the full additive method, a catalyst is first coated on a board. The portions of the board, which later become a pattern of interconnections, are then exposed, using a plating resist. An electroless plating film, which later becomes a pattern for interconnections, is then formed just by electroless copper plating for circuit pattern forming.
In addition to the above mentioned packaging techniques, a packaging technique, employing an ink jet method, is stirring notice these days in order to meet the demand for high density and a fine line diameter. This ink jet method is a non-contact direct patterning technique in which ink droplets formed by metal nano-particles are sprayed and applied from an ink jet printer head to plot a pattern of interconnections. With this technique, it is unnecessary to remove electroless plating or the catalyst in the subsequent process step, in distinction from the case of the semi-additive or full additive method, thus reducing the number of the process steps. In addition, disconnections resulting from removal of electroless plating chips may be eliminated. Hence, the technique is widely used these days in order to meet the request for high density and miniaturization (see Non-Patent Publication 1, for example).    Non-Patent Publication 1: Mari SAKAI, ‘Technique of Fabrication of Circuit Board by Ink-Jet Method’, Journal of Society of Electronic Information Communication, vol. 90, No. 7, pp. 544-548 (2007)    Patent Publication 1: JP Patent Laid-Open Publication H11-163499